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Sunday, December 16, 2012

Geysers of Enceladus photographed by the Cassini spacecraft. Credit: NASA

Last week, a proposal for a sample return from Enceladus described at
the American Geophysical Union conference received fairly wide-spread coverage
in the space-related press. The
descriptions generally were fairly short, however. Here, I’ll provide additional details from a
paper describing the mission that was published this past summer.

The mission, called Live Investigation for Enceladus (LIFE), would be a
descendent of the Discovery Stardust mission that captured dust grains from
comet Wild-2 during a flyby. The
Stardust spacecraft captured the grains in a disk of aerogel, which has exceptionally
low density for a solid. That low
density preserved most of the material of the grains despite the 6.1 kilometer
per second flyby. Several key members of
the Stardust team are principles in the LIFE proposal.

LIFE would replicate that method and add a second capture method to
return samples from the geysers of Enceladus, Saturns E ring (believed to be
formed from the material in the geysers), and the upper reaches of Titan’s
atmosphere.

The appeal of the mission is that it could return samples from a
potentially life-bearing subterranean ocean at Enceladus. Like Europa’s ocean, Enceladus’ ocean appears
to possess all the ingredients necessary for life: water, energy (the tidal
forces that are heating the icy crust for form the ocean), and contact with
rocky material that provides the elements needed for complex organic
molecules. (There are alternative
explanations for the geysers that don’t require an ocean, but the evidence
increasingly points to an ocean being the most likely source.)

While Europa’s ocean is sealed by kilometers of ice, Enceladus
conveniently spews an estimated 150-300 kilograms of water into space every
second. The grains, though, are tiny and
dispersed: Think of a particle of cigarette smoke every square meter by the
time the geyser’s plume are 80 kilometers above the surface. The small amount of material that could be
analyzed by a spacecraft flying through the plume would make chemical analysis
difficult for an instrument that must function within the mass, volume, and
power constraints of a spacecraft.
Instruments in Earth laboratories, however, would be able to make those
measurements. The goal of LIFE is to get
the ice grains to the laboratories.

Since the spacecraft would fly close to Titan and through the E ring on
its way to and from Enceladus encounters, it would collect samples from those
sources, too.

Capture of samples during flybys was considered by the Decadal Survey but the technical issues were considered daunting.

LIFE depends on several key elements to keep the total mission flight
time to less than 14 years (compared to previous estimates of 26 years) and the
costs within the Discovery budget (~$500M):

The mission would make use of one of the last available gravity assists
from Jupiter for a Saturn-bound mission by launching by 2019 (the next time the
planets are aligned correctly comes in 2058).

The spacecraft would enter Saturn orbit and use an unspecified number
of Titan flybys to enable flybys of Enceladus at between 2 and 3 kilometers per
second (compared to previous estimates of ~7 km/second)

A new form of aerogel, one-fifth the density of the aerogel carried by
Stardust, would be used. Between the low
encounter speed and the lower density aerogel, particles would experience a
factor of five lower effective entry impacts than the particles encountered by
Stardust. A rotating cover with a slit
on top of the aerogel disk would expose only a portion of the surface for each
flyby, allowing the source of each particle to be known.

A deposition system would provide a second sampling system that would
encase whole grains atop a film to better preserve complex and volatile
compounds. This system was originally
planned for the Stardust mission but dropped to reduce costs.

The sample would be kept at below freezing temperatures to preserve the
icy materials and any organic compounds

The spacecraft would also carry three instruments to conduct
measurements while in the Saturn system.
A much more capable mass spectrometer than that carried by Cassini would
make direct chemical measurements of the geysers, the E ring, and Titan’s upper
atmosphere. An infrared spectrometer
derived from the Rosetta VIRTIS instrument would both image Titan’s surface and
study the composition of its atmosphere and Encledus’ geysers. A camera, carried primarily for optical
navigation, would also image the dynamics of the geysers. Both spectrometers would be derived from
instruments developed in Europe; presumably the LIFE versions of these
instruments would be paid for by their sponsoring European nations, helping to
keep the mission’s costs within the Discovery budget.

Conceptual design for the LIFE spacecraft

Editorial Thoughts: This is a sweet concept being proposed by a team
that has shown that it can a deliver successful mission within the Discovery
budget.

The opportunity to sample an icy
moon’s ocean is unique to Enceladus and would come decades before any mission that
would reach pockets of Europa’s oceans.
The instrument suite would replicate that proposed for the Journey toEnceladus and Titan (JET) mission that had the goals of imaging Titan’s surface and
improving on Cassini’s measurements of the composition of Titan’s atmosphere
and the geysers. (The imaging
spectrometer would make use of spectral windows in Titan’s atmosphere to
improve on the coarse images possible with Cassini’s spectrometer. However, it’s not clear whether the
instrument proposed would match the resolution proposed for JET, and it’s not
clear how many encounters with Titan would be done.)

The basic techniques planned for LIFE could also be used for a poor
man’s comet sampling where a spacecraft would rendezvous with a comet and then
repeatedly fly through its jets to collect ice and dust particles at very low
velocities.

LIFE, however, faces several challenges in going from a concept to an
approved mission. First, to keep flight
times short, it may have to be selected in the next Discovery competition. Current and potential future budget cuts may
delay that competition until the mission could not be built in time to launch
in 2019. (The article does not discuss
fall back trajectories for reach Saturn.
They exist, but would take longer.
Each additional year of flight likely would cost another $7-10M per year
in operating costs.)

Another challenge is that the mission would take close to fourteen
years to return its paydust. (Sorry, pun
intended.) Other proposed missions would
return science much more quickly. The
instruments on board would provide data while the spacecraft orbits Saturn, but
the article doesn’t discuss how extensive the science campaign would be. If it were as extensive as that planned for
the JET mission, then that might make up for the long flight period.

The biggest challenge facing the mission appears to be one that the paper highlights:
the facilities that would house and handle the samples returned. Because life may exist within Enceladus’
ocean, the highest level of quarantine for the samples once they reached Earth
would be required. The paper’s authors
write, “the cost for planetary protection alone could exceed the cost estimate
for the proposed LIFE mission.
Consequently, the impact of planetary protection costs would have a
potential extinguishing effect on LIFE and other sample return missions.”

LIFE is a clever concept; I hope the authors find a way to resolve the
planetary protection issue. This concept is easily in my top two Discovery missions that I'd like to see fly.

I previously wrote about the LIFE proposal here. You can read the paper's abstract here.

Saturday, December 8, 2012

Much has been written about the announcement that
NASA will launch a second Mars Science Laboratory to Mars in 2020.Reactions have ranged from ecstatic to dumb founded
depending on where another Mars rover mission fits in each poster's priorities.

One criticism of the decision has been that NASA
has made it clear that caching samples for eventual return to Earth is a
possibility, but one that will compete with other scientific opportunities.There will be only so many dollars and so
much mass and volume available for the science payload.The Decadal Survey report, however, made it
clear that another Mars rover was a priority only if that rover the caching
element of a series of missions to return samples.

However, it appears that the President's Office
of Management and Budget (OMB) also has made it clear that they will not
support sample return with its $6-8B price tag.As one report put it, the James Webb Telescope's cost overruns have
soured OMB on multi-billion dollars space ventures.In other words, the Decadal Survey's number
one priority didn't get the sale.OMB
appears to be okay with Mars missions in general, so long as they are no more
than modestly expensive.In fact, Mars
offers advantages as a destination -- short flight times, lots of developed
technology, good science, proven public appeal.(My prediction: sample return will occur only if a rover finds organic pay
dirt that strongly hints at life, present or past.)

Why didn't NASA turn to the second ranked
priority, a Europa mission? We don't
know, but I'll speculate.The latest,
many flyby version of the mission has been costed to approximately $2B,
approximately half the cost estimate of an orbiter mission from a few years
ago.I believe that that cost doesn't
include the launch, which would add another 10% or more, taking the total cost
to more than $700M greater than the cost of MSL-2020 with launch.NASA's planetary program simply doesn't have
the funding for the current version of the Europa mission (or the third
priority, a Uranus orbiter).(When asked
when a Europa mission will fly, the head of NASA's science program said that
the cost would have to come down to the range of MSL-2020 (presumably including
the launch)).

Another option would have been to use the money
for MSL-2020 for a New Frontiers mission and a Discovery mission, which would
cost approximately the same amount (some additional funding probably would be
needed for the launches).Here, I
believe that NASA faced a strategic management decision.JPL is a unique asset for planetary
exploration.It needs a large mission to
keep its skills current and its workforce engaged.(If you're good enough to work at JPL, lots
of businesses would like your resume.)JPL might or might not win the competitions for the New Frontiers and
Discovery mission and the winning missions might not technically challenge JPL.

So, MSL-2020 fits the budget envelope, gives JPL
a major project, and will do good science (if not necessarily the top ranked
science from the Decadal Survey).In my
former career as a strategic planner for a large high tech company, I think I
would have advocated for the same decision in an era of declining budgets.As a private citizen, I would have preferred
to see the Europa mission fly, but MSL-2020 is a good consolation prize.

The announcement left some key questions
open.First, what is the budget for
developing the payload for MSL-2020?Technology advances since Curiosity's instrument selection means that
some awesome options are in development.Taking them to flight readiness, though, may require a substantial
budget.Working in a lab as a breadboard
is one thing.Guaranteed reliability on
the surface of Mars within a tight mass and volume constraint is another.

The answer to that first question will help the
mission's science definition team tackle the second question: What are the
scientific priorities for the mission?Take proven instruments to a new location?Deliver next generation instruments?Cache samples?I suspect that it may be a combination of the
three.One possibility might be to refly
some of the ExoMars instruments (which have the added benefit that they are not
paid for by NASA).I'd personally like
to see the ExoMars deep drill flown to get samples from well below the surface
at a second site to a sophisticated instrument suite.

Then there is the question of what follows
MSL-2020?This new rover fits within the
budget cap only because JPL has a substantial supply of flight ready
spares.Those won't be available for a
third MSL.Does NASA fly additional
missions to Mars in the 2020's or turn its attention elsewhere?Those decisions will need to be made well
before the next Decadal Survey is due around 2022.

And finally, what about the rest of the solar
system?By my reading of NASA's
projected planetary budgets, MSL-2020 consumes most of the budget once the Mars
MAVEN orbiter and InSight landers and the OSIRIS-REx asteroid sample return
missions launch.Without a budget
increase, follow on New Frontiers and Discovery missions to other targets may
be few and far between.I hope that
Congress' proposals to increase the planetary budget by $100-150M over OMB's
last budget proposal to Congress occur.That small amount per year could breathe new life into these smaller
mission programs.

I have found other good commentary (not all of which I agree with, but it's well reasoned and written) on NASA's decision at the following blogs: Vintage Space,

Thursday, December 6, 2012

The first week of December every year, I need to decide between attending two conferences, a forest ecology conference and the American Geophysical Union (AGU) conference. This year, I chose the latter, which was right for my current professional work, but wrong for my advocation, future planetary exploration planning. At AGU this year, NASA announced that it will fly a second Mars Science Laboratory (Curiosity) rover to Mars.My conference and a deadline for getting a draft of manuscript for a paper to co-authors has left me with little time this week. Phil Horzempa has stepped in with his account NASA's announcement. -------------------On December 4,
2012, NASA announced that they would launch an MSL-class rover to Mars in
2020.This decision helps to put some
clarity in NASA's Mars Exploration Program after years of uncertainty.Van has covered some of that turmoil in earlier
posts.

Now that the dust has
settled, we can look forward to two new exciting Mars rover missions in the
coming decade: ESA's ExoMars 2018 rover and NASA's MSL-2.Perhaps the split was unavoidable.To constrain costs, ESA and NASA tried
several options to conduct a joint rover mission.One mission plan was to deliver two rovers
(one from each agency) to the same landing site using a modified MSL-1
Skycrane.The latest incarnation called
for one, joint-effort, rover to be delivered to the surface of Mars via the
Skycrane.It seems, however, that the
rover may have been more of a European creation since ESA's ExoMars rover was
so far along in its development cycle.This would have meant that JPL's rover team would have little to do for
the foreseeable future.Its expertise
has been honed over a decade of Mars missions.One can conjecture as to why NASA withdrew from cooperation with ESA for
the ExoMars rover.One possibility is
that, in return for a large investment of funds, NASA was not going to be able
to maintain the team of artisans at JPL who designed and built MSL-1.They are a national asset.So, in the end, perhaps the Mars community is
better off with this split.Instead of two
rovers, or only one rover, at one site, there will now be two capable rovers
exploring two separate sites on Mars.

A recurrent plea in the planetary community has been for the
re-use of common spacecraft, i.e., don't keep re-inventing the wheel.It is heartening to see that NASA seems to
have accepted this idea, at least for now.Earlier this year, NASA chose the InSight Mars geophysics mission that
will re-use the Phoenix lander design.A
lot of effort went into transforming the Mars 2001 Lander into a robust,
well-tested soft lander.That system is
now ready to host Discovery-class payloads.Several ideas were presented at the Mars Concepts Workshop in June.The Phoenix spacecraft bus is a low-cost
means of getting to Mars' surface and we may see it used several times in the
coming decades.

MSL-2 not only will benefit from existing designs and testing but also from a supply of flight ready spares built for MSL-1, Curiosity.

This week, NASA chose to fly what is essentially MSL-2.NASA's chief of the unmanned Science

Directorate, John Grunsfeld, spoke about the decision at this
week's AGU meeting.Apparently, this
step has been cleared by the President’s Office of Management and Budget, which
approves NASA’s budget proposals

This mission will re-use the aspects of MSL-1 that took much
effort to design, develop and test.These include the large heat shield, the large parachute, the guided
entry system, the Skycrane, the MMRTG, and the actuators that caused so much
consternation.Instead of being abandoned,
these technologies will be used again.Therein lies much of the logic behind the reduced cost of MSL-2.In addition, the JPL team will get to apply
lessons-learned from their effort to build MSL-1.

There has been talk of a solar option for MSL-2.However, part of the cost savings for MSL-2
means taking advantage of the engineering that has already been done for MSL-1,
including the use of an MMRTG.If a
solar option were pursued, then a lot of systems engineering would need to be
re-done.For instance, MSL-1 utilizes
the heat from its RTG to warm its electronics during the bitter cold of Martian
nights.For the lowest cost and highest
performance, the MMRTG is the best option.

In fact, there appear to be a number of flight-qualified spares
from MSL-1, including an MMRTG, which could be used in MSL-2.The backup MMRTG seems to have been Pu-238
fueled already.If true, then that would
provide some answer as to the availability of Pu-238 for this mission.How that fuel would be utilized is still to
be determined since there will be a good amount of radioactive decay over the
next 8 years before launch.It may need
to be “mixed” with fresh Pu-238.

The subject of parts obsolescence will be addressed early
on.There are probably parts vendors
that either have gone out of business, or who no longer manufacture a given part.

As to whether this
mission could be moved up to 2018 with enough funding, there are otherconsiderations.Mainly, 2018 is not that far away and it
would be a tight squeeze trying to get the instruments built and tested by
then.A launch in 2020 actually allows a
greater variety of instruments to be considered for MSL-2's payload.

The launch window in
2020 is more favorable than the 2011 window used by MSL-1. This opens up more of the Martian surface to
landing site possibilities.

A Science Definition
Team will be assigned soon to define goals for the mission.In addition, an Announcement of Opportunity
for the instruments should be released this coming summer.Caching samples for Mars Sample Return is
open for debate.Scientists could decide
that resources on MSL-2 would be better utilized for in-situ studies.

Associate Administrator Grunsfeld pointed out that Mars
exploration presents an opportunity for synergy between NASA's manned and
unmanned flight programs.He pointed out
President Obama's challenge to fly a manned orbital mission to Mars in the
2030s.What this means for the MSL-2
mission is anybody's guess since he did not go into detail.However, the involvement of the agency's
manned flight effort could provide some funding support.It could also mean that some of the payload
would be aimed at providing data for future manned missions to the Red Planet.We already see this with the RAD instrument
on board MSL-1.

Dr. Grunsfled
mentioned that they could have flown a 2018 mission instead of the 2020 MSL-2,
but, because of the budget, it would have been a down-scaled orbiter.They decided to wait 2 years to get a surface
mission.The estimated cost of $1.5
Billion for MSL-2 includes a launch vehicle.

With reference to other aspects of NASA's unmanned Science
program, he indicated that NASA will continue to try to do a Europa
mission.Costs are getting almost low
enough for a new start, but they are not quite there yet.Van has written several posts reviewing the
efforts to design lower-cost Europa missions.

So, we now know the plan for NASA's Mars exploration over the
coming decade.One of the remaining
questions concerns the landing site for MSL-2.My vote is for a landing in, or near, Mariner Valley.It would allow for spectacular views and
science.

Sunday, December 2, 2012

Buried among the major announcements from the recently concluded
ministerial meeting were other decisions that may impact planetary exploration
in the coming decade. I discussed the
two most prominent of these decisions relevant to planetary exploration in my
last post; ESA approved the ExoMars joint implementation agreement with Russia,
and decided not to proceed with a German-backed lunar lander.

Buried in the news were two other items, one positive for planetary
exploration the other not.

I’ll start with the positive news.
ESA has viewed the ExoMars orbiter and rover missions as the first two
missions in what would be a continuing set of missions to explore Mars. The space agency has investigated a number of
possible missions for the first half of the 2020’s. Two missions could have been ESA’s
contribution to a joint Mars sample return mission with NASA: a precision lander with
a rover to fetch cached samples and/or an orbiter to collect the samples
delivered to Martian orbit and bring them back to Earth.With the delay (potentially indefinite) of
NASA’s contributions to a sample return, ESA has shelved these two concepts.

Two other concepts were approved for continued study by ESA for
potential launch in 2022 and/or 2024.
The Inspire geophysical network mission would deliver 3 landers to Mars
with a seismometer, a weather station, heat flow probe, and possibly other
instruments. (Details have not been
released, likely because the concepts appear to be in the earliest planning
stages.) This network of stations would
build on the single station geophysical NASA InSight mission (2016) and the
Russian geophysical station planned to accompany the ExoMars rover (2018). If either of these stations still operates if
and when the Inspire stations arrive, they would add additional nodes to the
network.

Inspire mission concept. Click on image for a larger version.

The second mission concept would be for a Phobos sample return mission
called Phootprint. Returning a sample of
Phobos, which may be accumulated rubble left from the formation of Mars or
rubble blasted off the planet by asteroid strikes, is a worthy scientific goal
in its own right. Russia attempted a
similar mission, and American scientists have proposed their own equivalent
missions several times for the Discovery program. In addition to the scientific goals, the
mission would also develop much of the hardware needed for the eventual Mars
sample return orbiter.

Phootprint mission concept. Click on image for a larger version.

The decision at the Ministerial mission was to proceed with mission
studies to better define the concepts and prepare them to enter
development. At the next Ministerial
meeting planned for 2015, ESA’s managers plan to seek approval to begin
development on one or both of the missions.

The less positive news for ESA’s science program was that the ministers
decided to freeze its budget for the next several years (after a small bump
from the contributions of two new ESA members).
Inflation will rob the science program of its purchasing power each year
at a projected rate of 2-3% per year.
One news article quoted and ESA science manager as saying that among the
options may be to delay to cancel a mission.
Typically, agencies push budget cuts onto the missions least far along
in selection or development. If ESA does
this, then either its next medium mission selection may be delayed or the JUICE
Jupiter-Ganymede mission may be pushed out.

The ExoMars mission may also impact the science budget. ESA has only one mandatory program, the
science program. Other programs, such as
the one that funds ExoMars and possibly Inspire and Phootprint, are optional
programs. To date, not enough funds have
been committed to implement the ExoMars missions. As a result, ESA management is looking at
possible contributions the science program could make. One idea is to have Russia supply the JUICE
launcher. That would save the science program
money late in this decade, but the ExoMars program needs funding mid-decade. Another idea is for the science program to
directly fund a portion of the ExoMars missions, which would conduct excellent
science. With that flat budget, though,
the potential for ripple effects to other science missions such as JUICE seem
possible.

You can download the presentation where I found the slides above from here.

About Me

You can contact me at futureplanets1@gmail.com with any questions or comments.
I have followed planetary exploration since I opened my newspaper in 1976 and saw the first photo from the surface of Mars. The challenges of conceiving and designing planetary missions has always fascinated me. I don't have any formal tie to NASA or planetary exploration (although I use data from NASA's Earth science missions in my professional work as an ecologist).
Corrections and additions always welcome.